Spatial distribution of glutathione, glutathione-related and antioxidant enzymes in cultured mouse embryos.

The present study was undertaken to evaluate the detoxifying capacity of organogenesis-stage murine concepti cultured in vitro. Investigative attention was particularly focused on the embryonic tissue distribution of cytoprotective pathways. Glutathione (GSH) status, GSH-related and antioxidant enzymes were assayed in the embryo proper (EP), visceral yolk sac (VYS) and ectoplacental cone (EC) of 29.44 +/- 1.56 (mean +/- SD) somite pairs concepti. All the tissues displayed significant and comparable concentrations of GSH, further supporting this tripeptide as critical in protection against embryotoxicants. The totality of enzymatic activities was detectable in the selected embryonic compartments. In terms of spatial distribution analysis, maximal activities were found in EC (glutathione peroxidase, glutathione reductase, superoxide dismutase and glyoxalase I and II), and VYS (glutathione transferase and catalase). These results indicate: (1) the organogenesis-stage conceptus, in addition to significant amounts of GSH, expresses constitutive activities of GSH-related and antioxidant enzymes; (2) maximal activity levels are detectable in the embryonic sites which, at the developmental stage selected for assay, serve (VYS) or are evolving to serve (EC) embryo/maternal exchange, and thus represent the primary sites of interaction with foreign compounds.